The present invention relates to devices and methods for measuring fluid flow in a duct.
Internal combustion engines today include electronic controls to provide optimal engine operation. Typically, the electronic control systems include a primary control unit for processing control algorithms and a variety of sensors for providing control signals to the primary control unit. One critically important sensor for achieving optimal engine control is a mass fluid flow sensor for measuring air intake into the internal combustion engine.
It is critical that the mass fluid flow measurement is accurate in order to provide optimal engine operation. One significant problem affecting the mass fluid flow measurement, is reverse flow or back flow in the direction opposite of fluid intake. Typically, mass fluid flow sensors detect the flow of air in both the forward and reverse directions relative to air intake, therefore reverse flow causes an inaccurate mass fluid flow reading.
Prior art mass fluid/air flow devices have attempted to address this problem by providing mass air flow sensor configured as disclosed in U.S. Pat. No. 5,556,340 issued to Clowater et al. In Clowater, a mass air flow sensor having a U-shaped air passage and a longitudinally converging elliptical inlet configuration is disclosed, and hereby incorporated by reference. This configuration increased measurement efficiency and reduced the effect of back flow on the measurement of air flow into the internal combustion engine. Further, such a configuration produces advantageously low signal to noise ratio, as well as high velocity across the mass fluid flow sensor element.
While prior art mass fluid flow sensors, such as the one disclosed in Clowater, significantly improved the accuracy of the mass fluid flow measurement. Improvements are still needed to address other problems.
For example, it would be advantageous to provide a mass fluid/air flow sensor having improved response time, a more aero-dynamic design, having a lower system pressure drop, an improved internal flow passage pressure drop, in improved signal to noise ratio, an improved electromagnetic interference performance, and fewer parts to achieve less manufacturing complexity.
In an embodiment of the present invention, a mass fluid flow sensor is provided for determining the amount of air inducted into an internal combustion engine, in accordance with the present invention. The mass fluid flow sensor of the present invention includes an external intake air temperature element which improves the accuracy of the mass air reading. An external cold wire element is further provided which improves response time. The mass fluid flow sensor of the present invention has an improved aerodynamic design which provides a lower system pressure drop. Moreover, the sensor is smaller and lighter and has fewer parts, thus providing a better manufacturability. For example, a molded one-piece isolated jet nozzle having a hot element disposed therein is provided in a tubular flow passage of the sampling portion of the housing. Consequently, an improved lower internal flow passage pressure drop is achieved. Additionally, an improved signal to noise ratio, as well as a larger dynamic range is an advantageous consequence of the present invention. The present invention further provides improved electromagnetic interference performance.
In an embodiment of the present invention, a mass fluid flow sensor having a circular opening or inlet of the nozzle is provided.
In another embodiment of the present invention, control electronics are located in a longitudinally extending section of the mass fluid flow sensor housing above the sampling portion. Thus, the present invention provides an integrated circuit cavity and sampling portion in one package.
In another aspect of the present invention, a U-shaped flow passage is provided having one constant radius bend r for capturing a sample of the intake air.
In yet another embodiment of the present invention, an outlet of the U-shaped flow passage is provided to allow the fluid to exit and flow out of the bottom of the flow passage, as well as, the sides of the housing.
In yet another embodiment of the present invention, a measuring element is located within the flow passage at the exit or outlet of the jet nozzle, in accordance with the present invention.
In yet another aspect of the present invention, the measuring element is centered at the exit of the converging nozzle.
In still another embodiment of the present invention, the control electronics are located adjacent the flow passage within the circuit cavity.
Further objects, features and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.